1. Field of the Invention
This invention relates generally to delivery systems for formulations comprising biologically active agents. In one embodiment, the invention relates to coated proliposomal formulations for poorly water soluble drugs.
2. Description of the Related Art
Pharmaceutical formulations may be administered through various routes of administration. For example, drugs may be administered orally, intravenously, subcutaneously and by aerosol. The encapsulation of pharmaceuticals in liposomes is useful in reducing toxicity and improving the therapeutic effectiveness of certain drugs. For example, compounds such as insulin, factor VIII, tryptophan, phenylalanine, heparin, vitamin K etc., have been investigated for their effectiveness orally, after encapsulation into liposomes. Although they represent an improvement over the prior art, oral liposome formulations have been criticized because of their instability, leakage and potential destruction in gastric fluids.
The use of proliposomes represents an alternative to conventional liposomal formulations. Proliposomes are dry, free-flowing granular products, which, upon the addition of water, disperse to form a multilamellar liposomal suspension. The stability problems associated with conventional liposomes, including aggregation, susceptibility to hydrolysis and oxidation, may be avoided by using proliposomes. The use of proliposomes is well-known in the pharmaceutical field.
Among the various routes of drug administration, the oral route is advantageous for some drugs in certain instances because of its versatility, safety and patient comfort. Although the oral ingestion of drugs represents a safe and versatile method of pharmaceutical delivery, the therapeutic efficacy of many drugs may be reduced because many pharmaceuticals are labile or inactivated under the acidic conditions of the stomach. Enteric coating materials have been applied to address this deficiency. Non-enteric coating also offer several advantages for both oral and non-oral routes of administration. Accordingly, the present invention, in some embodiments, provides novel formulations, coated with enteric or non-enteric coatings, and methods of making those formulations.